Re: Functions of two variables-doubt!

Posted by The Villain on Apr 21, 2014; 6:03am
URL: http://discussion-forum.276.s1.nabble.com/Functions-of-two-variables-doubt-tp7587463p7587504.html

Tangent plane at (a,b) will be given by
z-z1=del z/del x (x-a) + del z/del y(y-b)
We have z1=af(b/a)
now find del z / delx and del z/del y at (a,b)
we get eqn as
z-af(b/a)=f(b/a)-(b/a)f'(b/a)(x-a)+f'(b/a)(y-b)
the tangent plane will pass thtough origin if x=y=0
substitute the vlues x=0 and y=0
 we will get z=0
hence proved.. :-)